Merge pull request #135 from pwschmidt/master

MOBSDK-558/573/578
MOBSDK-590: There is no way to retrieve a rendition image for a document using an output stream
Merge branch 'master' of https://github.com/Alfresco/alfresco-ios-sdk into topic-MOBSDK-590
Merge pull request #136 from tmughal/master

MOBSDK-590
Merge branch 'master' of https://github.com/Alfresco/alfresco-ios-sdk
merged changes from Taz